1. Field of the Invention
The present invention relates to a control device for a fuel cell vehicle using a fuel cell and an electric storage device, which are connected parallel to each other, as a power supply for a driving electric motor. Particularly, the invention relates to a control of an output of the electric motor.
2. Description of the Related Art
As a control device, mounted on a fuel cell vehicle, for controlling a driving electric energy supplied to a driving electric motor for the fuel cell vehicle, for example, a control device constituted as shown in FIG. 6 is known.
The control device shown in FIG. 6 has a motor driver 101 for supplying a driving electric energy to a driving electric motor 100 and a fuel cell 102 functioning as a power supply for an electric accessory such as an air-conditioner (not shown). The control device is constituted in the following manner. A battery 103 is connected parallel to the fuel cell 102. If a response from a reactive gas supply unit 104 such as an air-conditioning compressor for supplying reactive gases to the fuel cell 102 is delayed and the reactive gases supplied to the fuel cell 102 are insufficient to cause a shortage of the amount of electric energy generated by the fuel cell 102, the shortage is compensated with an electric energy discharged from the battery 103.
The motor driver 101 supplies a driving electric energy depending on a torque command (TRQ_CMD) which is generated from an electric vehicle control unit 105 to the electric motor 100. The reactive gas supply unit 104 regulates the rate at which the reactive gases are supplied to the fuel cell 102 so as to obtain the amount of generated electric energy depending on a target output (PD_REQ) of the electric motor 100, the target output being calculated by a target output calculator 106.
In this instance, the target output calculator 106 calculates the target output (PD_REQ) of the electric motor 100 fundamentally on the basis of a requested output (PD_CAL) of the electric motor 100 determined depending on the rotational speed (Nm) of the electric motor and the amount of depression (Ap) of an accelerator pedal.
However, when the requested output (PD_CAL) exceeds a continuous output rating (PD_LMT) of the motor driver 101 or the electric motor 100, the target output calculator 106 limits the target output (PD_REQ) to the continuous output rating (PD_LMT) or lower to calculate the target output, thereby preventing the motor driver 101 or the electric motor 100 from running over the continuous output rating (PD_LMT). A torque command calculator 107 calculates the torque command (TRQ_CMD) for the motor driver 101 depending on the target output (PD_REQ). Consequently, the output of the electric motor 100 is suppressed to the continuous output rating (PD_LMT) or lower.
Therefore, when the driver of the fuel cell vehicle depresses the accelerator pedal in order to accelerate the fuel cell vehicle, the output of the electric motor 100 is suppressed to the continuous output rating or lower and a sensation of acceleration that the driver desires is not derived. The drivability may deteriorate. In order to prevent the drivability from deteriorating, the adoption of the motor driver 101 or the electric motor 100 with a higher continuous output rating is considered. In this case, there are the following disadvantages. Since the size of the motor driver 101 or the electric motor 100 is increased, a space for installation therefor is also increased. The cost of the motor driver 101 or the electric motor 100 also increases.